UNIVERSITY OF CALIFORNIA
COLLEGE OF AGRICULTURE
AGRICULTURAL EXPERIMENT STATION
PRINCIPLES GOVERNING THE CHOICE,
OPERATION AND CARE OF SMALL
IRRIGATION PUMPING PLANTS
C. N. JOHNSTONi
The development of agriculture in California depends almost
entirely upon the progress made in irrigation. Many thousands of
acres in the state would be unavailable for growing the crops giving
the higher returns, were it not for the water supplied by irrigation
pumping plants. All of the standard types of pumps are used to
some extent in irrigation. The four outstanding types now in use for
irrigation are the centrifugal, the deep well turbine, the screw, and
the plunger. Air-lift and rotary displacement pumps are found
occasionally, and serve only small irrigated areas.
GENERAL DISCUSSION OF PUMPS
Pumping for irrigation dates back to the beginning of history
when men or beasts of burden supplied the power that moved water
by one means or another. Many machines were developed in Egypt
and India for this purpose long before the age of mechanical power ;
today some of these are used in modified form in California. With
the invention of the steam engine and the demands made by coal-mine
owners for better pumping machinery late in the eighteenth century,
progress in the mechanical powering of pumps began. Since this
time the use of mechanical power as applied to pumps has increased
rapidly. Today in California about one-sixth of the electrical power
Junior Irrigation Engineer in the Experiment Station. Eesigned July 16, 1926.
Z UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
produced in the state is consumed in driving irrigation pumping
equipment. This does not take into consideration the pumps driven
by fuel-oil engines.
Pumping originally consisted of filling some sort of container or
carrier by immersion in a body of water and then transporting the
retained water to a higher elevation. Some pumps use this process
today. Others are not immersed in the source of supply at all but
are connected with it through a suction pipe only. In these instances
the operation of the pump creates a reduction of pressure, or partial
vacuum, within itself, causing the water at the source to be forced
into the pump by the greater pressure of the air outside. The amount
of vacuum or reduction in pressure that must be produced in order
to raise the water to the pump is roughly equal to the pressure that is
produced by a column of water equal in height to the vertical distance
between the center of the pump and the surface of the supply water.
A perfect vacuum is a total lack of pressure, and if such a condition
is created in a pump, the water will rise from the source a vertical
distance of about 34 feet, at sea level. This distance decreases as the
elevation above sea level increases, because the weight of air diminishes
with increase of elevation. It is not desirable to place an irrigation
pump more than 15 to 20 feet above the water source, because friction
in the suction pipe consumes some of the pressure difference created
by the pump when in operation.
Every mechanical contrivance wastes a certain amount of power
within itself in the performance of its task; this is of course true of
all pumping equipment. The power delivered by pumping equipment
divided by the power supplied to it gives a ratio which, when
expressed as a percentage, is known as the efficiency of the plant. In
other words, the efficiency of a pumping plant is a measure of its
behavior while in operation. When the efficiency is low, the. pumping
cost is higher than it should be, because more power is being wasted
than is necessary.
Pumps located above the source of water supply must be capable
of 'drawing' the water to them when they are started empty, or if
incapable of so doing, both the pumps and the suction lines must be
filled with water previous to starting; that is, they must be primed.
This is accomplished by the use of a hand pitcher-pump or equivalent
power-driven unit, connected to the highest point of the pump case,
by means of which the air is withdrawn from the pump and suction
pipe. The discharge valve being closed during this operation, the
water rises from below and replaces the air as the latter is withdrawn.
CIRC. 312 J OPERATION OF SMALL IRRIGATION PUMPING PLANTS 3
Or, the priming may be accomplished by filling the pump and suction
pipe with water from some available supply, a flap valve being located
at the bottom of the suction pipe to prevent the loss of the priming
water. When the first method is used, the discharge valve is opened
automatically or by hand as soon as the pump is started. If the
second is used, the flap valve, or foot valve, opens automatically as
soon as the pressure of water above is relieved. Pumps whose operat-
ing parts are submerged in the source of supply require no priming.
The types of pumps used in irrigation in California obtain their
names largely from their method of applying power to the task of
moving water. Of the chief types used for irrigation, the centrifugal
was the first produced in this country, having appeared in Boston
in 1817. It was called the Massachusetts pump and was made very
crudely. It had as an impeller four straight paddles or vanes, which
have been replaced in the modern pump by the curved vanes, forming
smooth passages for the water. Its principle of operation, however,
was the same as that of the present-day centrifugal pump, the water
in both cases being forced through openings in the impellers by
centrifugal action caused by their high speed of rotation. In the
centrifugal pump, in other words, as the water is thrown out of the
impeller it creates the partial vacuum necessary to draw in more
water and thus continue the operation.
Centrifugal pumps may be obtained to operate against low or
high lifts, and to discharge almost any desired quantity of water.
When they have been purchased to fit the operating conditions, they
show very good efficiencies. Because these pumps are accessible at
all times and can be inspected and kept in repair, the efficiency may
be maintained indefinitely unless the impellers are subject to excessive
wear from abrasive material in the water.
The cases, or housings, of these pumps are supplied either as solid
or as split castings (fig. 1). The solid type has a plate bolted on the
side, which, when taken off, permits the removal of the shaft with the
impeller on it. The split type opens on the center line of the shaft,
exposing bearings, shaft, and impeller. In either case, the impellers
may be of the open or closed type. The former type is more common
with the single-suction solid-case pumps. Open impellers, as the name
implies, are simply impeller vanes mounted or cast against one disk
or hub. Closed impellers have their vanes mounted between two disks.
4 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
They provide better guidance for the water than the open type and
are generally more efficient.
The suction-pipe connections in these two types differ, as a rule.
In the solid-case pump, the suction pipe enters the center of one
side of the case, so that the water passes into the center, or throat,
of the impeller on one side only. In the split-case pump, the suction
line is in the same plane as the impeller, at right angles to the shaft,
and the pump casing is so built as to lead the water around both sides
Fig. 1. — Typical pumps. (1) Split-shell centrifugal pump opened for inspec-
tion; (2) single-suction centrifugal pump opened for inspection; (3) deep well
turbine model with runners and shaft exposed, full-sized bowls and runner
being shown in front; (4) single screw from deep well pump; (5) rotary dis-
placement priming pump. (The pump appears just above the number.)
CIRC. 312] OPERATION OF SMALL IRRIGATION PUMPING PLANTS 5
of the case into the two throats of the impeller. Double entry of the
water into the impeller tends to balance the thrust of the water stream
entering it — a considerable advantage for this type of construction
not usually obtained in the single-suction pump. Previously the
solid-case pumps were often made with two suction pipes, accom-
plishing the same result as the present split-case pump with its
divided channels within the case. Special thrust bearings are fre-
quently placed in both types of pumps to take up any unbalanced
forces on the impellers.
The losses in efficiency in centrifugal pumps are attributable to
air leaks, water slippage, and undue churning of the water. The first
cause may be eliminated through occasional inspection of the packing
glands and suction-line connections. The second, in so far as possible,
is taken care of by correct design, all passageways that can permit
leakage between discharge and inlet of the impellers being made as
narrow as possible, and in some cases being made extra long by the
insertion of grooved rings. For this reason, an impeller should not
be allowed to rub on the side of the case because of the resulting wear,
which is accompanied by excessive internal leakage. Churning, the
third cause of low efficiency, is the natural result of operation and
may be corrected only in part by proper design and correct speed of
rotation. This last factor is especially important because the cen-
trifugal pump is designed to operate at a given rotative speed against
a given lift, and to throw a predetermined quantity of water. When
the speed is changed, therefore, from that for which it is designed,
the pump cannot show its best performance. Churning often arises
where the pumping lift has remained constant and the discharge has
been increased by raising the speed of rotation of the pump consider-
ably above the rated number of revolutions per minute.
As has been previously stated, irrigation pumps not immersed in
the supply source should be located not more than 15 to 20 feet above
that source, and for this reason, as the water level recedes, the pumps
must be lowered or they cease to operate. In most cases when cen-
trifugal pumps are used to lift water from wells, they must be set
in pits at the time of installation. These pits are expensive to con-
struct and are often dangerous. It is desirable to make them as
small as possible. For these and other reasons, centrifugal pumps
have been developed with vertical shafts which permit their operation
from the ground surface. Pumps with long shafts which are often
used in deep pits, however, are subject to much trouble, and, conse-
quently have been largely replaced by the deep well turbine and
other true deep well types.
UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
DEEP WELL TURBINE PUMPS
The turbine pump is a form of the centrifugal, in which the pump
case contains stationary curved diffusion vanes that lead the water
away from the impeller to the discharge opening with a minimum of
turbulance, receiving the water from the impellers at high velocity
and passing it on with reduced velocity and increased pressure. Deep
well turbines (fig. 1) have been developed to meet the requirements
associated with pumping from wells of limited diameter. They are
built to operate on a vertical shaft with a single unit or bowl, or with
several mounted in series, one above the other, the stationary curved
vanes in the case turning the water from the impeller upward to the
bowl above, or to the discharge column pipe.
Because this form of pump is limited in size by the well it must
enter, it is necessary to forfeit part of the good characteristics of
operation possible in the centrifugal or turbine not so limited, but
giving an equivalent discharge. For instance, under present practice,
the deep well turbine may be operated against a head of about 25 feet
per bowl, or stage, whereas the centrifugal or turbine designed for
use outside a pit may be capable of operating at triple this head per
stage. This is the reason for mounting several bowls in a series in a
deep well turbine when the pumping lift is more than 25 feet. The
present tendency in design is for higher rotative speeds, resulting
in higher heads and greater discharge capacities per bowl. The deep
well turbine is always mounted with the bowls below the surface of
the standing water in the well, so that it is always ready to operate
without priming. This distinct advantage is offset, however, by the
fact that these rapidly rotating parts are buried in the well, and very
often receive no attention until they fail to operate. Since minor
adjustments are likely to be needed in any mechanism that rotates
at high speed, the efficiency of the deep well turbine is often lowered
because repairs are not made, owing to the inaccessibility of its
Considerable difficulty arises from the fact that power for the deep
well turbine must be transmitted through a long shaft. Manufacturers
have adopted many expedients for overcoming this difficulty. Some
pumps have enclosed drive shafts, in which the bearings of bronze
or other special material are mounted, while others eliminate the
bearings entirely and provide wooden guides which extend practically
the whole length of the shaft, to prevent flopping or whipping. Others
ClRO. 312] OPERATION OF SMALL IRRIGATION PUMPING PLANTS 7
accomplish the same result by placing rubber guides or bumpers at
intervals along- the otherwise exposed shaft. These do not require
oiling (fig. 2).
The lubrication necessary to these long drive shafts, which are
mounted on bearings, is accomplished by several means. Some shafts
are made hollow in order to carry oil to the bearings; others use the
drive-shaft housing for this purpose. The bottom bearing of the
deep well turbine is of such great importance that a special line is
Open bearing in
spider frame screwed
info pump co/umn
bearing joining fyvo
sections of drive shaft
Drive shaft bousing
Drive sbofl, no bearings
■Dpi 'it yyood liner yvitb
bo/byv core for s-faft
Metallic bousing for
liner and drive shaft
Metallic spider frame
screwed into pump
"column and supporting
-Various types of shaft-bearing construction for deep well
sometimes run down outside the pump to effect its lubrication. In
other instances, the bearing is packed with grease when assembled
and is repacked only when repairs become necessary. Since all of
these devices are liable to failure, they should be inspected whenever
possible. Rapid deterioration of bearings often results from gritty
materials which are contained in the water being pumped and which
become mixed with the lubricating oils.
These turbine pumps may be purchased for either belt or direct
connection to the power unit for lifting water any desired distance.
Some installations at present approach lifts of 500 feet. When kept in
good condition mechanically, they operate with very good efficiency.
UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
The screw-type pump is an application of the principle used by
Archimedes to move water upward on an inclined plane turning on
a movable shaft. There are several types of the screw pumps in use
in irrigation. All involve fundamentally a rapidly rotating- section
of an inclined plane, although some have several planes on a common
hub. Their action in water is the same as that of an electric fan in
air, which slides the air forward from its rotating, inclined vanes
(fig. 1). Some are used for heads of less than 10 feet, moving large
quantities of water ; others are used for medium to high lifts in wells.
The low-lift screw pump falls into two classes, those whose drive
shafts are horizontal and those whose shafts are vertical. The units
with horizontal-drive shafts are very large and are used where large
quantities of water are to be raised a short distance. The low-lift
screws on vertical shafts are mostly smaller-capacity ditch pumps,
which lift the water a few feet out of the ditch onto the land. Some
of these pumps are very crudely made, being merely a screw mounted
at the lower end of a shaft enclosed by a rectangular housing and
supported on one bearing placed at the top. Their efficiency is low,
and were the lift greater they could not be operated at all because
the cost of power would be too high. Other designs set in carefully
planned housings and having substantial bearings show very good
efficiencies, and because of their simplicity, are readily repaired and
kept in gcod condition.
The deep-well form of screw pump is a series of low-lift pumps
so mounted on a single shaft that they operate as a unit. They are
assembled from sections about 6 feet long. Each section has two
screws mounted in it with a single bearing which is supported in a
spider frame between the two screws. The planes of the spider tend
to keep the water from whirling as it travels upward. A second set
of vanes is placed above the upper screw in each unit to stop the
whirling action of the water leaving that screw. When it is desired
to pump against a head at the surface of the well, a number of screws
are nested at the bottom of the pump because the total lift per screw
cannot exceed about 4 feet and should be about 2 x /2 to 3 feet, under
which conditions this type of pump operates with very good efficiency.
Screw pumps are subject to the same difficulties as the deep well
turbines with their long shafts transmitting the power. Since it is
impossible to line the drive shaft and bearings with screws located
UlRC. 3 12 J OPERATION OF SMALL IRRIGATION PUMPING PLANTS 9
along the length of the shaft, the bearings are open to the entry of
abrasive substances in the water. This disadvantage is balanced by
the adaptability of these pumps to changing water tables, because
sections of pump added at the top or removed from the top, as the
conditions dictate, will enable the pump to follow the water levels.
In contrast, the turbine requires complete withdrawal for changing
the bowls whenever a lowered or raised water table necessitates it.
As in the case of the turbines, the screw pump is liable to be operated
when repairs should be made. It requires no priming, since the
operating parts are immersed in the water supply. As a general rule,
screw pumps will handle more water than deep well turbines of the
same outside diameter.
Joe f ion
Fig. 3. — Simple plunger pump.
The plunger pump may be obtained in many styles, but its use in
irrigation is limited by the fact that its capacity is relatively small.
Fundamentally all plunger pumps are pistons sliding in close-fitting
chambers (fig. 3) with two valves so arranged that one opens when
the piston creates a partial vacuum in the chamber, the other being
forced shut. The reverse occurs when the piston creates a pressure
in the chamber. The suction line connects to the port over the valve
that opens under vacuum and the discharge line connects to the port
over the valve opening under pressure from the piston. The many
designs of plunger pumps, both power and deep-well types, are all
applications of the fundamental type either for use in wells or for
service at the surface of the ground.
Deep well plunger pumps are used in areas where only a
limited supply of water is available at a considerable depth, supply-
10 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
ing water to a limited area per pump. They operate very efficiently
against any head when new and if moving clear water, but they are
subject to excessive wear along the close-fitting surfaces if the water
contains abrasive material. They require constant attention under
these conditions as they soon cease to function economically after
wear starts. They do not need to be primed to start pumping if they
are in good condition. In fact, small plunger pumps are used as
priming units for centrifugal installations.
The air-lift pump, as its name implies, uses air to lift or float the
water from the source of supply. A compressor injects the air, which
is sent to the bottom of the pump through a line of pipe let down
vertically into the water. The pipe enters the bottom of the larger
pump pipe column (fig. 9) . The air carries out with it as it rises to the
top of the pipe, a certain amount of the water. For correct operation,
at least two-thirds of the length of the pump must be below the surface
of the water supply. When the discharge is at some point above the
ground surface, a still greater portion must be submerged. Even with
the best of conditions, an air-lift pump has a very low efficiency. Its
application in irrigation is, therefore, very limited. It should find
increasing use, however, in the development of wells, since there are
no moving parts to be injured by abrasion.
ROTARY DISPLACEMENT PUMPS
The rotary displacement pump is another device limited somewhat
in irrigation use by lack of capacity. Though it is made with many
forms of internal design, all are dependent upon the rotary motion
of eccentrically shaped or gear-like impellers that turn in the pump
case in close-running fit. Because of their shape, they mesh to seal
off part of the water in the case at a certain point in their revolution
and then, turning further in mesh, eject the water into the discharge
pipe (fig. 1). As they are capable of creating a considerable partial
vacuum if they are kept in good condition, they do not need to be
filled with water to start pumping, provided they are not too far above
the supply source. They are occasionally used to prime centrifugal
pumps. Because the action of the pump depends upon the close fit of
the impellers, the inclusion of abrasive material in the water being
moved is disastrous to their operation. They require constant atten-
tion if the water they handle carries such material, this being their
ClRC-312] OPERATION OF SMALL IRRIGATION PUMPING PLANTS
chief disadvantage. They show a good efficiency Avhile the running
parts are tight but drop off rapidly when wear starts. This type of
pump is not applicable to deep well pumping.
It is the custom of salesmen in speaking of a pump to refer to its
curve sheet. Such a sheet is very useful because it gives a graphic
picture of the operation of the pump in question. Figure 4 gives
curves for one pump at the given speed and the efficiency discharge
curve of a second at that same speed. To use the curves one proceeds
in the following manner :
200 300 400 £00 600 700
Discharge in gat/ons per minute
Fig. 4. — Curve sheet for centrifugal or deep well turbine pump; speed 1165
r.p.m. The solid lines refer to the first pump. The dotted line is the efficiency
curve for the second pump, which shows an undesirable curve for conditions of
varying pumping heads. Each curve represents the relationship of two factors;
e.g., each of the curves labelled "Plant efficiency — Discharge" represents the
relationship of the efficiency of one of the plants to its discharge.
First, note that the three solid-line curves are drawn for a pump
when turning at 1165 revolutions per minute, for which speed it was
designed and at which speed it operates best, If driven at any other
speed, this pump will have different sets of curves. Also note that
the horizontal base line is scaled to read discharge in gallons per
minute, while the vertical line indicates pumping head, plant effici-
ency, and horsepower to motor.
The most important thing shown in the plant-efficiency — discharge
curve for the first pump is that when the highest point of efficiency
12 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
or 60 per cent, is reached at 460 gallons per minute discharge against
98 feet pumping head, the input horsepower to the motor will be
18.5 horsepower. If the head pumped against is not at this point,
the efficiency is lower. The single dotted line indicates the efficiency-
discharge curve of the second pump. It illustrates a. characteristic
design, in which a small change in head or discharge will create a large
change in efficiency, as compared to the first pump whose efficiency
curve is not so steep. It is evident, therefore, that the second pump
is less desirable than the first where pumping lifts are likely to vary.
A prospective pump owner, then, should buy a pump having a flat-
topped efficiency-discharge curve, if his water levels are liable to vary.
Where constant lifts are assured, a sharp-pointed efficiency curve is
not objectionable, if the point of maximum efficiency fits the operating
conditions. When pumping lifts are sure to increase, the pump should
be purchased to operate, when first installed, at a point to the right
of the point of maximum efficiency rather than to the left. The
operating conditions will then become constantly better for a time
THE SELECTION OF MACHINERY
The above description of the different types of irrigation pumps
has indicated that each type is adapted to some particular condition,
such as high or low water table, or large or small discharge. There
are, however, so many makes of pumping plants available that the
buyer is often at a loss to determine which to select. He should first
consider his power unit, which will be driven through a belt if a fuel-
oil engine is selected. Since pumping is a steady load on an engine,
the latter must be large enough to drive the pump. Unless over
capacity is allowed, the life of the engine is materially shortened.
This is particularly true in the case of light-duty engines such as
those coming from pleasure cars. If an electric drive is to be used,
the buyer must determine whether it is to be direct or belt connected.
Though both connections have advantages, the direct insures positive
speed maintenance and eliminates some loss. The make of pump
selected should depend upon the service obtainable from the sellers in
the given area, provided that the products of several reputable manu-
facturers are represented.
A standard form of agreement 2 to cover the sale and purchase
of irrigation pumping equipment has been drafted by a committee
2 Moses, B. D., and L. S. Wing. Farmers' Purchase agreement for deep well
pumps. California Agr. Exp. Sta. Bui. 448:1-46. 1928.
CIRC. 312] OPERATION OF SMALL IRRIGATION PUMPING PLANTS 13
representing the pump manufacturers, the California Farm Bureau
Federation, and other organizations. No buyers should fail to' see
that his sale contract follows the standard form. Since this agree-
ment is in substance a guarantee of the performance of the plant
purchased, it affords protection to sellers and manufacturers, as well
as consumers, throughout the state. Some satisfactory form of written
agreement as to performance should be given with every purchase of
As was indicated earlier in this circular, there are two sources
of water for irrigation, namely, surface and underground waters.
Underground supplies are located in the gravels and sands laid down
by the streams of ancient times. They are supplied by percolation
from the rains and streams of the present day, mainly the latter.
Many of these streams of years ago sprang from the same hills and
mountains as those of today. The beds of the present streams,
therefore, often cut the old gravel and sand deposits on the mountain
sides and much of the water in the stream sinks into them, to be
recaptured only by pumping.
Because these gravels and sand strata are often supplied by waters
flowing at a high elevation, they are sometimes found in the valley
floor under sufficient hydraulic pressure to cause the water to flow out
of the well. Most of them are under some hydraulic pressure, so that
the water rises part way up the well casing, at least, when the strata
are encountered. Wells of this type are called artesian wells whether
they flow or not. Since the water travels slowly through these water
strata, irrigation pumping often tends to take the water faster than it
can be supplied. The pressure in the strata is thus reduced and the
pumping level lowered. When the draft is large, this lowering is
often felt in every well drawing from the same strata. Unless the
winter rains and the streams can replenish the supply during slack
pumping periods, the drop may become permanent. The water table
may continue to be lowered in heavily pumped areas until pumping
The sinking of wells to develop underground waters has led to the
production of a special class of machinery. A large soil auger is used
to bore into the earth. Sometimes a scow or sand bucket is oscillated
up and down in earth and water in the hole, gathering in a certain
part of this mixture through a flap valve located at the bottom. Heavy
drills or rock bits that pound their way downward are used in areas
,4 Scow or Sbnd pump
3 duger or boring too/
C Pope sochef
D Pope sockef sub
£ Uars or /iommers
F Scow or fbmp *?ub
O Pock bif
Fig. 5. — Types of well-drilling tools used in California.
ClKC. 312J OPERATION OF SMALL IRRIGATION PUMPING PLANTS
where rock or boulders are encountered, the loosened material being
brought to the surface with a sand bucket. Heavy drilling is further
aided by the use of massive jars or hammers, which give an additional
blow upon the bit or scow (fig. 5). These tools are operated by well
Fig. 6. — Typical well rig used for heavy drilling. Note scow being dumped.
rigs, consisting of a portable power plant with a tower at one end
(fig. 6), over which a cable is run for the operation of the scow or
similar tools, and for the withdrawal of the auger-type tools. The
augers are actuated by a turn table, powered through a chain or belt
16 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
drive from the well rig. The hole made by the drilling tool is gener-
ally lined with metallic casing forced down as rapidly as space is
provided for it below.
Casing is usually either screw-joint pipe or so-called * stove-pipe'
casing. Both may be obtained for almost any sized well. Stove-pipe
casing is made from No. 18 or thicker sheet-iron in 2-foot sections
which are lapped over each other for half their lengths to form a pipe
whose surfaces are smooth inside and out, and whose walls are a
double thickness of the sheet metal used. Variations of these two
types are in use, but not generally in California. One of these, a
single-riveted casing, is used to some extent in the smaller wells. It
is made of a single thickness of fairly light sheet-iron.
While the well is being drilled, a record must be kept of the
position of the water-bearing strata encountered, in order that the
casing may be perforated in these areas. Perforating is done by the
well rig, unless manufactured perforated casing has been obtained
for direct insertion into the well while drilling is in progress. Many
contrivances have been used to perforate casing, including both
cutting knives and punches, but none have been found entirely satis-
factory. Some wells are never perforated. These depend upon the
flow attainable from the bottom opening alone and are called open-
bottom wells. It is only occasionally, however, that a sufficient supply
can be obtained from this opening alone. On the other hand, it is
common to seal the bottoms of wells taking their supply through
perforations, making them closed-bottom wells. The perforations
are slits or regular-shaped holes in the walls of the casing and are
arranged more or less uniformly about the circumference of the well
opposite the water-bearing strata. Unless sufficient openings are made
in the casing, the resistance to flow through it will be excessive, and
the water will be unduly lowered, thereby increasing pumping costs.
One special form of well consists of a hole large in diameter
and sunk with a rotating auger or drill, from which water is
ejected. The water washes the loosened materials from the well.
Into this hole a casing of smaller diameter is inserted, the outside of
which is surrounded with coarse clean gravel. This method is used
to provide a greater area of entrance for the ground-waters, since the
whole casing may be perforated. The clean gravel cylinder on the
outside permits easy access to the water. The drilling process, how-
ever, may puddle the walls of the well, thus defeating the purpose
somewhat. In some localities where the materials penetrated are
self-supporting, wells may not require casing.
CIRC. 312] OPERATION OF SMALL IRRIGATION PUMPING PLANTS 17
Almost all wells when first completed require developing. That
is, they must be pumped for a considerable time to draw the fine
particles of earth away from the water strata into the well and out
through the discharged stream. After the fine particles have been
removed from the water strata, the flow usually increases, because the
water can pass through the strata more readily. The discharged water
also becomes clear. As has been previously suggested, the air-lift can
be used very satisfactorily for developing wells because it has no
moving parts. Deep wells should be developed before the pumping
equipment is ordered. Such a practice would greatly lengthen the
life of the equipment. The pumps would then operate at higher
efficiencies, since they could be purchased to meet known conditions
of operation, and would not be subjected to the abrasion incident to
the development of the wells.
WELL AND PUMP TESTS
After a well has been developed, it should be tested to determine
the depth to water when the desired discharge stream is being
obtained. This is important because these measurements indicate the
character of the well. If possible, the test pump should be run at
several different speeds, readings of discharge and depth to water
being obtained for the well while the pump is operating at each speed.
In this way, the actual tendency of the well can be determined and
the pumping lift for any discharge can be estimated. This type of
data is plotted as a curve (fig. 7) enabling one to know fairly accur-
ately what the probable conditions of operation will be beyond the
range of the observed data.
The curve in figure 7 is typical of nearly all wells in California.
That is, the water stands in the well at a certain depth ; when pumping
is in progress, this depth increases as the amount being discharged
increases. The amount of change in depth, or draw-down, with
changing discharge is not the same for all wells, but depends upon
the ease with which the water passes through the water-bearing strata
and the well perforations. The more easily the water moves into the
well, the smaller will be the change in water level for any given
discharge rate. The guesswork usually practiced for determining
these data cannot possibly fit a pump to a given well accurately.
It is as important to test the new pumping plant when it is in
place as it is the developed well. Since there is always a chance for
a slip in the installation of machinery of any type, it is to the advant-
UNIVERSITY OF CALIFORNIA — EXPERIMENT STATION
age of the owner, seller, and power company to test every new pump
installed. Such a test should cover the following items: discharge,
pumping lift, power requirement, and, of general interest but not
entirely necessary, the speed of rotation of the pump and motor.
Discharge may be obtained as follows: Allow the discharge from
the pump to fall into an open ditch, across which has been constructed
a bulkhead with a weir notch, similar to that shown in figure 8.
Make sure that the ditch is large enough so that the water may
approach the weir without undue haste or turbulence. Be sure that
30O 350 400 450 500
Discharge in Oollons per Minute
Fig. 7. — Curve resulting from plotting well-test data.
the weir crest is horizontal and the bulkhead perpendicular to the
ground. Place a small stake a few feet back from the weir and
beside one bank of the ditch, with its top just level with the crest of
the w r eir, as shown in figure 8. A carpenter's level may be used to
set the stake correctly in relation to the weir crest. A ruler held
perpendicularly with the zero end resting on the top of the stake will
indicate the depth of water flowing over the weir. The discharge may
be determined by inspection of the accompanying weir table (table 1).
The flow in gallons per minute for weirs of different widths is
indicated opposite the readings of head in inches, as measured on the
stake in the wier pond. The flow found in the table corresponding to
the measured head for the weir used is the discharge for the pump.
CIRC. 312] OPERATION OF SMALL IRRIGATION PUMPING PLANTS
The method of measuring the pumping lift varies somewhat with
different types of pumps, on account of the different uses and mount-
ings. In the case of such pumps as the centrifugal, whose suction and
discharge lines are completely accessible, the following methods of
measurements are followed. A vacuum gage is mounted on the suction
pipe as near the pump as possible ; if the discharge line extends to
some distance from the pump, a pressure gage is tapped into it also,
%W^ bulkhead set
\\\:^Kjnto d/'fch bank
Beye/ed edge of
yve/r up stream
top or~ stoke /eve/ with ""^
cr&st of weir
8. — Rectangular weir in place. A indicates necessary clearance of
five or more inches between edges of weir and ditch banks.
close to the pump. The sum of the readings of these two gages con-
verted into feet, plus the vertical distance between the centers of the
gages, gives the pumping lift. If the water is discharged from the
pump close at hand, the pumping lift becomes suction-gage reading in
.feet, plus the vertical distance from the suction-gage center to the
center of the discharge pipe at its highest point.
In the case of pumps whose suction and discharge lines are inacces-
sible, the pumping lift may be calculated roughly from pipe-friction
tables, adding the measured vertical distance between the highest
Discarge Table for Eectangular Weirs
per minute for crests of various
7 7 /l6
n l A
CIRC. 312] OPERATION OF SMALL IRRIGATION PUMPING PLANTS 21
point of discharge and the supply water surface. Such figures are
useful only for making a rough check of the operation of a pumping
For pumps such as the deep well turbines installed in such a way
that their suction lines are inaccessible, but whose discharge lines may
be tapped, measurement is made of the distance in feet from the ground
surface to the surface of the supply water. To this is added the vertical
distance from the ground surface to the center of the discharge pipe at
its highest point, if the discharge is close to the pump. If it is not, a
pressure gage must be tapped into the discharge line and its reading
in feet must be added to the vertical distance in feet between the
center of the gage and the ground surface, plus the vertical distance
in feet between the ground surface and the supply- water surface.
Manufacturers of deep w T ell turbines consider the part of the dis-
charge column pipe below ground as a portion of the pump, making
the pumping-lift readings as obtained above acceptable.
The measurement of the vertical distance between the ground and
water-supply surface may be obtained only through the use of a
sounding line (fig. 9). This may be an electrically insulated wire
with an exposed end let down into the well so that it will ground in
the water, making a complete circuit with a bell ringer in it. Measure-
ment of the length of line will give the depth to water. On the other
hand, it may be an air line of pipe of known length run down into
the well with the pump. Air is forced into this line and the maximum
pressure obtainable is recorded in pounds or feet on a gage at the sur-
face (fig. 9). Some of these gages read the number of feet to water
direct. Those reading in pounds must be corrected to feet by multi-
plying the reading by 2.31 (1 pound equals 2.31 cubic feet of water).
This number of feet indicates the submersion of the end of the air
line. Subtracting the submersion in feet from the total length of the
line in feet gives the distance to water. Example : A 120-foot air line
in a well being pumped requires 13 pounds air pressure to force the
water out of the line. The pressure goes no higher than 13 pounds,
because the air escapes at the bottom as fast as more is added when
this point is reached. Thirteen pounds equals 13 X 2.31 feet of water
or 30.03 feet of water (call it 30 feet), the submersion of the end of
the air line. Therefore, the depth to water is 120 feet less 30 feet, or
90 feet. A direct reading pressure gage scaled in feet would have
indicated 90 feet immediately under these conditions. All pump
installations should be designed to permit measurements of the depth
of water. Special precautions must be taken to make this possible in
placing deep well pumps.
line @" pipe)
yvoter /'eye I
Fig. 9. — Diagram
of air-lift pump in
well, showing two
methods of sound-
ing depths in wells.
\4/r iine from compressor
enters pump column
ClEG. 312] OPERATION OF SMALL IRRIGATION PUMPING PLANTS
The power input may be measured readily in the field only for
electrically driven units. Although the power companies will be glad
to assist in this measurement, the owner can determine it for himself
after ascertaining the number of watts registered by the electric meter
in his pumping plant for each revolution of the aluminum disk
(fig. 10). He should be sure that the figure furnished in watts
includes any special set-up constants for the installation. After this
WATT HOUR METER
of f/v's cf/^k
Fig. 10. — Electric-meter indicating disk. In making a pumping-plant
test, the revolutions of this disk are to be counted.
figure, commonly known as a disk constant, is obtained, the number
of revolutions of the aluminum disk should be counted for several
minutes and the total divided by the exact number of minutes counted.
This figure should be multiplied by the constant obtained from the
power company, and the result multiplied by 60 and divided by 746.
The final figure is the horsepower being supplied to the motor. With
the completion of this step, the over-all, or plant efficiency, may be
computed as follows : Multiply the discharge in gallons per minute by
24 UNIVERSITY OP CALIFORNIA EXPERIMENT STATION
the weight of a gallon of water (8.33 pounds) and multiply this by
the distance the water is lifted, in feet. Then divide the result by
33,000. The result is horsepower represented by water pumped.
The plant efficiency is the important item to the user, since it tells
how well the whole unit is working. From the buyer's viewpoint the
seller should specify the plant efficiency when indicating the char-
acteristic of operation. The over-all or plant efficiency is the water
horsepower output divided by the electrical horsepower input, with
the result multiplied by 100. Checking the speed of an electrically
driven unit will occasionally demonstrate a faulty motor, but this
condition is seldom found. Plants not electrically driven may be
tested to determine the discharge, the head pumped against, and the
speed of rotation. The last named requires the use of a speed counter,
which most pump-installation men have in their equipment. If the
pump is up to the speed specified, it should deliver the quantity of
water indicated by the seller for the head being pumped against.
Tests of an irrigation pumping plant should be made occasionally
throughout its life so that the necessary adjustments may be made
to maintain a satisfactory efficiency.
DISCUSSION OF FIELD CONDITIONS
Operators of irrigation pumping equipment have always felt
somewhat dissatisfied with the cost of operation and the performance
of their pumping equipment. In order to determine the sources of
this dissatisfaction, investigations were conducted in the field during
parts of 1924, 1925, and 1926. These consisted of field tests of many
pumping plants, conducted in as thorough a manner as possible. All
measurements were checked by several readings, which were averaged.
All gages were checked for accuracy and in several instances electric
watt-hour meters were tested by the power companies to make certain
of their accuracy. These instruments were seldom found more than
1 per cent in error by the company tester. Wherever possible, weirs
were used in making readings of discharge and when their use was
impossible, every effort was made to insure accuracy by checking
several methods against each other. Soundings to water in the wells
were made, where possible, with an insulated wire which completed
an electric circuit with a bell ringer in it when contact was made
with the water. Occasionally, an air line of known length was avail-
able and sounding was made with it, checking with the electric
sounder wherever this could be done. Tables 2 and 3 indicate in
CIRC, 312] OPERATION OF SMALL IRRIGATION PUMPING PLANTS
general the results of these tests, showing the average operating con-
ditions for the three types of pumps tested. These figures might vary
a few points either way, were they for another set of pumping plants,
but they represent a fair cross-section of the irrigation pumping
plants supplied by wells. They are probably typical of the whole
state, since they were taken in a number of areas.
Eesults of Field Tests of Irrigation Pumping Plants
Deep well turbine
gals, per minute
Approximate Characteristics of Air Lift, Plunger, and Eotary
gallons per minute
It will be noted in the tables above that the average discharge of
the centrifugals is considerably higher than for the other two types
tested. This is due to the inclusion of several 10 and 20-second-foot
units among the centrifugal-pump tests. These plants were about
twenty years old, and their efficiencies were still considerably above
the average for the type. They were much older than any of the
screw pumps or deep well turbines tested. The centrifugal pumps
of capacity corresponding to the other two types showed about the
average efficiency of their type. In many cases the small centrifugals
fell considerably below the average for the type. Plant efficiencies
for the three types ranged from 15.2 per cent in several cases to 70
per cent in one case.
The discouraging feature of the tests was that so many plants
should be operating at one-half or less than one-half of the average
efficiencies for the type. It is apparent that the average efficiencies
26 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION
Fig. 11. — Typical deep-well pumping plant in house.
CIRC. 312] OPERATION OF SMALL IRRIGATION PUMPING PLANTS 27
are not ideal, since they represent conditions of power waste amount-
ing to over one-half that furnished. Were the lowest efficiencies up
to the average for that particular type, the owner's power bill would,
in some cases, be less than half what it is. Such conditions are largely
chargeable to failure on the part of the owner to keep his equipment
in good running order. There is little excuse for centrifugals to go
far below their normal efficiency because they are accessible at all times
and repairs are simple. The other two types, as has been mentioned,
are more difficult to inspect and to repair. However, efficiencies as
low as some of those found indicate that occasional tests will pay for
themselves by calling forth the necessary repairs.
The burden of fault does not rest entirely upon the owners of
these plants showing low efficiencies, because the manufacturing and
sales agencies have been responsible for some of this trouble. Their
equipment has not always stood up in service as it should, because
makeshifts in construction have been employed. Part of these make-
shifts are the result of efforts on the part of manufacturers to attain
a low sale price for their products in order to meet competition.
Such practice is not countenanced by the more reputable manufac-
turers, but the individual buyers of pumping equipment often mistake
poorly made machines for bargains. The electric motor or the electric
distribution system may be responsible for low efficiencies of operation
in pumping plants, but this is the exception rather than the rule.
When an operator has become suspicious of his electrical equipment,
he should first make sure that the fault is not in the pump.
Centrifugal pumps are simple and are easily cared for. They are
located on ground-surface foundations or in open pits, as a rule. They
are best fitted to operate where the water supply is readily approach-
able, as in the case of surface waters or shallow underground supplies.
When correctly installed, their efficiency should be good.
Deep well turbine pumps are much like the centrifugals in per-
formance, but they are not so easily inspected and kept in repair.
They may be used to pump water from almost any depth, and if
inspected and repaired occasionally, should show good operating
Screw-type pumps lend themselves to a variety of applications
including both long and short lifts. Its characteristic is its large
capacity. In the deep well units, it is hampered in its performance
28 UNIVERSITY OP CALIFORNIA EXPERIMENT STATION
by the fact that it is not easily inspected. Its efficiency is good if it
is inspected and repaired occasionally.
The air-lift pump has as its chief asset its simplicity and lack of
wearing- parts, thus making it suitable for use in developing wells.
Its application to irrigation is limited to special conditions because
of its low efficiency.
Because they are limited in capacity, the plunger pumps are
used generally in irrigating comparatively small tracts. There are
many areas with deep water supplies of limited capacity served
largely by this type of pump. Plunger pumps are also limited in
use by the fact that abrasive materials in the water supply soon cut
them out, destroying their otherwise very good efficiency.
The rotary displacement pump is very similar to the plunger
pump in its application to irrigation. It has the same limitations as
the latter and also it can be used only where there are surface or
shallow underground waters.
To be satisfactory, plant efficiencies should not be below 50 per
cent. A large number of plants in the field operate considerably
below this figure. Many are doing so because their owners or operators
have failed to inspect and repair them as they should. Some pumps
are so poorly made that they cannot maintain nor even attain 50 per
cent plant efficiency. These units may be eliminated through proper
selection by the bivyers.
New plants should be placed only in a developed well and should
be tested for operating efficiency. Check tests should be made
throughout the life of all plants.
STATION PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION
253. Irrigation and Soil Conditions in the
Sierra Nevada Foothills, California.
262. Citrus Diseases of Florida and Cuba
Compared with those of California.
263. Size Grades for Ripe Olives.
268. Growing and Grafting Olive Seedlings.
273. Preliminary Report on Kearney Vine-
yard Experimental Drain, Fresno
276. The Pomegranate.
277. Sudan Grass.
278. Grain Sorghums.
279. Irrigation of Rice in California.
283. The Olive Insects of California.
294. Bean Culture in California.
304. A Study of the Effects of Freezes on
Citrus in California.
810. Plum Pollination.
312. Mariout Barley.
813. Pruning Young Deciduous Fruit
819. Caprifigs and Caprification.
324. Storage of Perishable Fruit at Freez
325. Rice Irrigation Measurements and
Experiments in Sacramento Valley,
328. Prune Growing in California.
331. Phylloxera-Resistant Stocks.
835. Cocoanut Meal as a Feed for Dairy
Cows and Other Livestock.
339. The Relative Cost of Making Logs
from Small and Large Timber.
840. Control of the Pocket Gopher in
343. Cheese Pests and Their Control.
344. Cold Storage as an Aid to the Mar-
keting of Plums.
346. Almond Pollination.
347. The Control of Red Spiders in Decid
348. Pruning Young Olive Trees.
349. A Study of Sidedraft and Tractor
350. Agriculture in Cut-over Redwood
353. Bovine Infectious Abortion.
354. Results of Rice Experiments in 1922.
357. A Self-mixing Dusting Machine for
Applying Dry Insecticides and
358. Black Measles, Water Berries, and
Related Vine Troubles.
361. Preliminary Yield Tables for Second
362. Dust and the Tractor Engine.
363. The Pruning of Citrus Trees in Cali-
364. Fungicidal Dusts for the Control of
365. Avocado Culture in California.
366. Turkish Tobacco Culture, Curing and
367. Methods of Harvesting and Irrigation
in Relation of Mouldy Walnuts.
368. Bacterial Decomposition of Olives dur-
369. Comparison of Woods for Butter
370. Browning of Yellow Newtown Apples.
371. The Relative Cost of Yarding Small
and Large Timber.
373. Pear Pollination.
374. A Survey of Orchard Practices in the
Citrus Industry of Southern Cali-
375. Results of Rice Experiments at Cor-
376. Sun-Drying and Dehydration of Wal
377. The Cold Storage of Pears.
379. Walnut Culture in California.
Growth of Eucalyptus in California
Pumping for Drainage in the San
Joaquin Valley, California.
Pollination of the Sweet Cherry.
Pruning Bearing Deciduous Fruit
The Principles and Practice of Sun-
Berseem or Egyptian Clover.
Harvesting and Packing Grapes in
Machines for Coating Seed Wheat with
Copper Carbonate Dust.
Fruit Juice Concentrates.
Crop Sequences at Davis.
Cereal Hay Production in California.
Feeding Trials with Cereal Hay.
Bark Diseases of Citrus Trees.
The Mat Bean (Phaseolus aeon it if o
Manufacture of Roquefort Type Cheese
from Goat's Milk.
Orchard Heating in California.
The Blackberry Mite, the Cause of
Redberry Disease of the Himalaya
Blackberry, and its Control.
The Utilization of Surplus Plums.
Cost of Work Horses on California
The Codling Moth in Walnuts.
The Dehydration of Prunes.
Citrus Culture in Central California.
Stationary Spray Plants in California.
Yield, Stand and Volume Tables for
White Fir in the California Pine
Alternaria Rot of Lemons.
The Digestibility of Certain Fruit By-
products as Determined for Rumi-
Factors Affecting the Quality of Fresh
Asparagus after it is Harvested.
Paradichlorobenzene as a Soil Fumi-
A Study of the Relative Values of Cer-
tain Root Crops and Salmon Oil as
Sources of Vitamin A for Poultry.
Planting and Thinning Distances for
Deciduous Fruit Trees.
The Tractor on California Farms.
Culture of the Oriental Persimmon
Poultry Feeding: Principles and
A Study of Various Rations for
Finishing Range Calves as Baby
Economic Aspects of the Cantaloupe
Rice and Rice By-products as Feeds
for Fattening Swine.
Beef Cattle Feeding Trials, 1921-24.
Cost of Producing Almonds in Cali-
fornia ; a Progress Report.
Apricots (Series on California Crops
The Relation of Rate of Maturity to
Apple Growing in California.
Apple Pollination Studies in Cali-
The Value of Orange Pulp for Milk
The Relation of Maturity of Cali-
fornia Plums to Shipping and
Economic Status of the Grape Industry.
The Selection and Cost of a Small
The Control of Citrus Insects.
Melilotus indica as a Green-Manure
Crop for California.
Oidium or Powdery Mildew of the
Control of the Pear Scab.
Small Fruit Culture in California.
The County Farm Bureau.
Fertilizing California Soils for the
The Construction of the Wood-Hoop
The Packing of Apples in California.
Factors of Importance in Producing
Milk of Low Bacterial Count.
County Organizations for Rural Fire
Peat as a Manure Substitute.
The Function of the Farm Bureau.
Salvaging Rain-Damaged Prunes.
Feeding Dairy Cows in California.
Methods for Marketing Vegetables in
Testing Milk, Cream, and Skim Milk
The Home Vineyard.
Harvesting and Handling California
Cherries for Eastern Shipment.
Winter Injury to Young Walnut Trees
The Apricot in California.
Harvesting and Handling Apricots
and Plums for Eastern Shipment.
Harvesting and Handling Pears for
Harvesting and Handling Peaches for
Marmalade Juice and Jelly Juice from
Central Wire Bracing for Fruit Trees.
Vine Pruning Systems.
Some Common Errors in Vine Prun-
ing and Their Remedies.
Replacing Missing Vines.
Measurement of Irrigation Water on
Supports for Vines.
The Use of Artificial Light to Increase
Winter Egg Production.
Leguminous Plants as Organic Fertil-
izer in California Agriculture.
The Control of Wild Morning Glory.
The Small-Seeded Horse Bean.
Thinning Deciduous Fruits.
Sewing Grain Sacks.
Cabbage Growing in California.
Tomato Production in California.
Preliminary Essentials to Bovine
Plant Disease and Pest Control.
Analyzing the Citrus Orchard by
Means of Simple Tree Records.
The Tendency of Tractors to Rise in
Front; Causes and Remedies.
An Orchard Brush Burner.
A Farm Septic Tank.
California Farm Tenancy and Methods
Saving the Gophered Citrus Tree.
Head, Cane, and Cordon Pruning of
Olive Pickling in Mediterranean Coun-
The Preparation and Refining of Olive
Oil in Southern Europe.
The Results of a Survey to Determine
the Cost of Producing Beef in Cali-
Prevention of Insect Attack on Stored
Fertilizing Citrus Trees in California.
The Almond in California.
Sweet Potato Production in California.
Milk Houses for California Dairies.
Potato Production in California.
Phylloxera Resistant Vineyards.
Oak Fungus in Orchard Trees.
The Tangier Pea.
Blackhead and Other Causes of Loss
of Turkeys in California.
The Basis of Grape Standardization.
Propagation of Deciduous Fruits.
The Growing and Handling of Head
Lettuce in California.
Control of the California Ground
The Possibilities and Limitations of
Coccidiosis of Chickens.
Buckeye Poisoning of the Honey Bee.
The Sugar Beet in California.
A Promising Remedy for Black Measles
of the Vine.
Drainage on the Farm.
Liming the Soil.
A General Purpose Soil Auger and its
Use on the Farm.
American Foulbrood and its Control.
Cantaloupe Production in California.
Fruit Tree and Orchard Judging.
The publications listed above may be had by addressing
College of Agriculture,
University of California,